Mercury switch with lighted trigger



Oct. 15, 1957 I E. F. REIHMAN ,81

MERCURY SWITCH WITH LIGHTED. TRIGGER Filed Nov. 50, 1955 Zr/ FEei/zman ilnited States Patent 2,810,047 MERCURY SWITCH WITH LIGHTED TRIGGER Earl F. Reihman, Warwick, R. I., assignor to General Electric Company, a corporation of New York I This invention relates to electric switches and in particular to a double-pole mercury button switch with a lighted trigger.

A mercury button switch may be defined as that type of electrical switching device containing one or more mercury buttons rotatable to an on or off position. Conventionally, a mercury button comprises a pair of hat-shaped metal shells separated by an insulating bar rier having a passageway therein and an outer glass ring forming a hermetic seal between the shells. When the metal shells and barrier are rotated to a predetermined position, mercury stored between each shell and the bar rier passes through the passageway in the barrier to establish electrical contact. between the shells and thereby act as a switching device. The mercury buttons used herein are of a conventional type as described, for example, in U. S. Patent No. 2,101,093 which is assigned to the same-assignee as is the present invention.

The present invention isprimarily concerned with a double-pole mercury switch of the general type shown in the Sambleson Patent No. 2,142,153 which is also assigned to the same assigneeas the present invention. This type of switch is sometimes referred to as a three-way switch, and it is used in pairs to control a load in a circuit from two different locations. A single-pole mercury switch having a lighted trigger is taught by the Courtney Patent No. 2,434,065 which is now assigned to the same assignee as is the present invention. Consequently, my invention has resulted froman attempt to provide a double-pole mercury switch with a lighted trigger. Such a switch has a pair of mercury buttons in side-by-side relationship and it is necessary to connect one lead wire of the lamp in the hollow trigger to the inner shell of one of thebuttons. This is, done by following the teachings in the above-cited Courtney patent whereby the overlying trigger holds the bare lead wire in contact 'with the shell. The other lead wire of the lamp joins with a series resistor that is in turn to be connected with the outer shell of the other button. I have devised for this purpose a novel spring clip of wire form which has one end hooked in a groove of the shell while the other end of the clip extends around the periphery of the shell and terminates behind the hook end so that the lead wire will be held down by the clip to be in contact with, the shell. ,The unstressed size of the clip-is smaller in di? ameter than the diameter of the shell so that it is necessary to spring the clip open in order to install it on the shell. I

The results obtained from my spring clip were quite unusual and unexpected for it was found necessary to grasp the clip at three or more places around the shell in orderto' remove. it, because it.holds so well. The hooked end of the clip .which is seated. in the groove digs 'in and servesas a semi-permanent pivot means. It'is for this reason that the opposite end of the clip must be placed behind the hook end of the clip for it is the hook end that holds the free end of the clip from slipping oil? the shell. It the free end were inadvertently placed in front 2,810,047 Patented Oct. 15, 1957 of the hook end, it would not be possible to predict whether the clip would stay in place during use or not.

Accordingly, it is the principal object of this invention to provide a mercury button switch with a novel spring clip for connecting a lead wire to the shell of one of the buttons.

A further object of this invention is to provide a double-pole mercury switch having a lighted trigger with a novel adjustable means for connecting the lead wires of the lamp with the proper shells of the buttons.

A further object of this invention is to provide a novel spring clip of wire form in a mercury button switch for connecting a lead wire to one shell of the button.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing': a

Figure 1 is a side elevational view of a double-pole mercury switch with a lighted trigger embodying my invention.

Figure 2 is a transverse cross-sectional view taken on the lines 2-2 of Figure 1.

Figure 3 is a plan view of the switch of Figure 1 with the trigger, mounting strap and cover plate removed in order to expose the interior of the switch. I Figure 4 is an isometric view showing merely the relationship of the two mercury buttons and the connections between the lead wires of the lamp and the shells of the buttons.

Figure 5 is a circuit diagram including a lamp load and a pair of three-way switches that have lighted triggers which are energized when the circuit is open.

Figure 6-is a view of the spring clip of my invention in its unstressed condition.

Referring in detail to the drawing and particularly to Figure 1, the switch embodying my invention comprises a deep recessed base 10 of suitable molded insulating material, a trigger 11 for manually operating the switch, an insulating cover plate 12 fitting over the trigger and substantially closing the top opening of the base to protect the internal switch parts, and a conventional metal mounting strap 13 fastened by suitable screw means 14 to the switch base for supporting the switch in a wall mounted switch box in the usual manner.

Turning now to a consideration of the interior view of the switch of Figure 3, it is apparent that the switch isprovided with three exposed terminals, namely, 15 and 16, and common terminals 17 which are joined by the connecting strap 18 within the base. Binding screws 27 are mounted in tapped openings in these terminals as in standard double-pole mercury switches. These terminals areformed as integral parts of spring contacts of strip'material which are vertically arranged in parallel relation within the base. Terminal 15 is joined with contact 15' while terminal 16 has a contact portion 16' and the common terminal 17 has a pair of contacts 17. Identical mercury buttons 19 and 20 each comprise a pair of opposed hat-shaped metal shells 21 which are separated by a perforated insulating barrier (not shown) and formed into a sealed container by'the. outer glass seal 22 as will be well understood by those skilled in this art. The spring contacts of the switch 15', 16' and 17 each have a semi-spherical bump at its free end for engaging in the semi-spherical concavity 23 in the crown of the shells. As an example, the button 19 is rotatably supported. between the contacts 15 and 17 while the button Zilis supported betweenthe contacts 16 and 17 insulatingfipartition 24 extends up from the bottom wall of the base so that the contacts 16' and 17' are braced thereagainst. In order to assemble these parts in the switch base, it is first necessary to place each button between its supporting contacts and then lower them into the base for there are small clearances between the side walls and 26 of the base and the separating partition 24 when the contacts and buttons are in place as shown in Figure 3.

The trigger 11 as shown in Figure 2 is hollowed out so that a neon glow lamp 30 may be placed therein. A molding compound is used that will result in a translucent trigger which will literally glow to indicate both that the circuit is open and the location of the switch in a dark room. For this purpose an ivory colored trigger is preferred. As best shown in Figure 4, one lead wire 31 of the lamp is to be connected with the inner shell of the mercury button 20. A series connection is made by the other lead wire 32 of the lamp with a current limiting resistor 33. Finally, an insulated lead wire 34 connects the resistor to the outer shell of the mercury button 19. Here I have shown my novel spring clip 35 extending around the periphery of the outer shell of the button for holding the bent end of the lead wire 34 in contact therewith as will be better understood hereinafter.

The trigger 11 is formed with a pair of saddle portions 36 each of which is supported on the adjacent inner shell of the buttons 19 and 20 for suspending the trigger therebetween. Conventionally, the shells of mercury buttons are each provided with a transverse groove 37 so that a standard button may be used in all types of mercury switches. 36 of the trigger has a lug (not shown) seated in the groove 37 of the inner shells of the two buttons so that the trigger is in driving engagement with the buttons. Thus, as the trigger is moved manually the buttons rotate about their common axis for opening and closing the circuit. Accordingly, it will be clear that the free end of the lead wire 31 is held in electrical contact with the inner shell of the button 20 by the downward force exerted by the saddle portion 36 of the trigger in the manner taught in the above-cited Courtney patent.

I have taken advantage of the groove 37 in the standard mercury button to design an adjustable spring clip 35 which will grip the shell much better than a simple washer for instance. This spring clip 35 is of wire form having one end formed with an inwardly turned hook end 38 adapted to be seated in the groove 37 of the shell, while the opposite end 39 overlaps the hook end that is usually provided with an upturned portion 40. This clip in its unstressed condition, as shown in Figure 6, is of smaller diameter than the diameter of the shells of the buttons so that in assembling the clip to the shell, it is necessary to force it on, thereby putting the clip under tension. Caution must be exercises as to two particulars, namely, the hook end 38 must be engaged in the groove 37 of the shell to prevent its rotation and, secondly, the overlapping end 40 must terminate behind the hook end to be adjacent the center of the button as opposed to its side. It is then an easy matter to take the insulated lead wire 34 and hook it under the overlapping end 40 of the clip to locate it as shown in Figure 4 of the drawing. This also applies additional tension to the clip, thereby increasing its resistance to its removal from the shell.

Having described my invention of a novel spring clip for attaching a lead wire to the shell of a mercury button, it will be readily appreciated by those skilled in this art that a mercury button switch embodying my invention for use with an illuminated trigger is both simple in design, low in cost and ingenious in operation. Reliability of operation was of primary concern although ease of assembly and minimum cost of manufacture were also important considerations that were solved by this invention.

Modifications of this invention will occur to those skilled in this art; therefore, it is to be understood that this invention is not limited to the particular embodiment In this particular case, each saddle portion fl. disclosed but that it is intended to cover all modifications which are within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A mercury button switch comprising a hollow housing with a pair of spring contacts rotatably supporting a mercury button therebetween, said button including at least one metal shell forming a part of sealed container for the mercury, and means for connecting a lead wire to the periphery of the shell comprising a spring clip of wire form having one end hooked in a slight depression in said one shell while the other end of the clip extends around the periphery of the shell and terminates behind the said hooked end, the unstressed size of the clip being smaller in diameter than the diameter of the shell so that it must be forced onto the shell whereby a lead wire may be hooked under the spring clip and held in electrical connection With the shell.

2. A mercury button switch comprising a hollow housing with a pair of spring contacts for rotatably supporting a mercury button therebetween, said button including a perforated insulating barrier separating a pair of opposed hat-shaped metal shells to form a sealed container for the mercury, each shell of the button having a groove in its periphery, and a hollow trigger supported for driving engagement in the groove of one of the shells, an indicator lamp mounted in the trigger, and means for connecting one lead wire of the lamp to the periphery of the other shell of the button including a spring clip of wire form having one end hooked in the groove of the shell while the other end of the clip extends around the periphery of the shell and terminates behind the said hooked end, the unstressed size of the clip being smaller in diameter than the diameter of the shell so that it must be forced onto the shell, whereby the lead wire is hooked under the spring clip and held in electrical connection with the shell.

3. A double-pole mercury switch comprising a hollow housing having a pair of mercury buttons each rotatably supported between a pair of spring contacts to move on a common axis, each button including a perforated insulating barrier separating a pair of opposed hat-shaped metal shells to form a sealed container for the mercury, each shell having a groove in its periphery and each groove being aligned transversely of the housing, a hollow switch trigger of translucent material supported on the inner shells of the buttons and having a lug seated in the grooves theerof for driving engagement between the trigger and the buttons, and a mounting strap fastened to the housing to hold the trigger in operative relation with the buttons, an indicator lamp mounted in the trigger ,with one of its terminals in electrical connection with the inner shell for one of the buttons by the downward force exerted by the trigger on the shell, a current limiting resistor in series with the lamp, said resistor having an insulated lead wire for connection with the outer shell of the other button, and means for connecting this lead wire to the shell comprising a spring clip of wire form having one end hooked in the groove of the shell while the other end of the clip extends around the periphery of the shell and terminates behind the said hooked end, the unstressed size of the clip being smaller in diameter than the diameter of the shell so that it must be forced onto the shell, whereby the spring clip holds the free end of the lead wire connected to the shell.

References Cited in the file of this patent UNITED STATES PATENTS 992,993 Russell May 23, 1911 1,464,602 Garcillan Aug. 14, 1923 1,865,207 Persons June 28, 1932 2,434,065 Courtney Jan. 6, 1948 

